Preparation method of shield type anion exchange membrane with acid resistance

Abstract

The invention discloses a preparation method of a shield type anion exchange membrane with acid resistance, and belongs to the field of wastewater treatment. The acid barrier layer and the traditional AEM substrate are chemically bonded, so that the inherent contradiction between the conductivity of the AEM and the acid barrier property is successfully solved. Aiming at the special requirement of a bipolar membrane electrodialysis process on the acid resistance of a membrane material, polyvinylidene fluoride is creatively adopted as a hydrophobic framework material, and polyethyleneimine containing a weak base group is introduced to a main chain of the hydrophobic framework material through a grafting reaction, so that the PVDF-g-PEI composite membrane material with a side chain structure is successfully prepared. According to the design, a unique membrane microstructure is constructed and comprises a microphase separation domain and an internal cross-linked network, so that the acid resistance of the membrane is remarkably improved, meanwhile, relatively low membrane surface resistance is kept, and a high-performance membrane material solution is provided for a BMED process.

Description

Technical Field

[0001] The present invention belongs to the field of wastewater treatment, and particularly relates to a preparation method of a shield-type anion exchange membrane with acid resistance performance. Background Art

[0002] As an innovative solution in the field of pharmaceutical acid crystal wastewater treatment, bipolar membrane electrodialysis (BMED) technology has achieved a double improvement in environmental and economic benefits through a circular economy model of "treating waste with waste", and has become one of the core technologies to promote the green transformation of the pharmaceutical industry and the implementation of the carbon neutral goal. However, the large-scale industrial application of this technology still faces multiple challenges: the high costs of bipolar membranes and electrodes, the decline in operating stability due to insufficient anti-pollution performance of membrane materials, and the non-compliance of product purity. Among them, the proton penetration phenomenon of traditional anion exchange membranes (AEMs) will cause serious counter-ion migration, which not only reduces the system current efficiency, but also makes it difficult to increase the acid chamber concentration, becoming the core technical obstacle restricting acid concentration enrichment.

[0003] Currently, research on the inhibition of proton penetration shows that based on the proton-carrier co-transport mechanism involving water molecules, technical means such as introducing hydrophobic groups, constructing a dense membrane structure, and modifying weak basic groups are mainly used. For example, grafting fluorocarbon segments can reduce the proton permeability by 40%-60%, and constructing a cross-linked network structure can increase the acid retention rate to more than 90%. However, these modification methods often come at the cost of membrane conductivity. This trade-off in electrochemical performance severely limits the actual application effect of the technology. Therefore, the development of a new type of AEM with both high acid barrier properties and low surface resistance has become the key to breaking through the bottleneck of the industrial application of BMED technology. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a preparation method of a shield-type anion exchange membrane with acid resistance performance.

[0005] The present invention provides a preparation method of a shield-type anion exchange membrane with acid resistance performance. By chemically bonding an acid barrier layer to a traditional AEM substrate, the inherent contradiction between the conductivity and acid barrier performance of AEMs is successfully solved. In view of the special requirements of the bipolar membrane electrodialysis (BMED) process for the acid resistance of membrane materials, the present invention innovatively uses polyvinylidene fluoride (PVDF) as a hydrophobic backbone material, and polyethyleneimine containing weak base groups is introduced onto its main chain through a grafting reaction, successfully preparing a PVDF-g-PEI composite membrane material with a side-chain structure. This design constructs a unique membrane microstructure, including microphase separation domains and internal cross-linked networks, which not only significantly improves the acid resistance of the membrane, but also maintains a low membrane surface resistance, providing a high-performance membrane material solution for the BMED process.

[0006] A preparation method of a shield-type anion exchange membrane with acid resistance performance, specifically completed according to the following steps:

[0007] I. Preparation of PVDF-g-PEI:

[0008] ①. Dissolve polyvinylidene fluoride, polyethyleneimine, tris(2-pyridylmethyl)amine, and CuBr2 in a reactor containing N,N-dimethylformamide. Then add polished copper wire to the mixed solution, introduce nitrogen into the reactor to remove the air in the reactor, and then seal the reactor under a nitrogen atmosphere.

[0009] ②. Place the reactor in a constant-temperature oil bath and heat for a period of time, then immerse it in an ice bath system to terminate the reaction, obtaining a reaction mixture; add the reaction mixture to an ethanol solution for precipitation, filter and remove the remaining polished copper wire to obtain a solid reaction product; dissolve the solid reaction product in N,N-dimethylformamide, and then add it to an ethanol solution for precipitation for purification, filter, and vacuum dry at room temperature to obtain PVDF-g-PEI.

[0010] II. Preparation of PVDF-g-PEI membrane:

[0011] Dissolve PVDF-g-PEI in N,N-dimethylformamide, then cast it onto a flat glass plate, and then place it in a vacuum oven to dry for a period of time. The membrane detaches from the glass plate. Finally, immerse the membrane in an HCl solution for protonation to obtain a PVDF-g-PEI membrane, and store the PVDF-g-PEI membrane in the HCl solution.

[0012] III. Preparation of anion exchange membrane:

[0013] ①. Dissolve polyvinylidene fluoride and polyethyleneimine in N,N-dimethylformamide, stir for a period of time, then add azobisisobutyronitrile, and then cast it onto a flat glass plate, and then place it in a vacuum oven to dry for a period of time. The membrane detaches from the glass plate. Finally, immerse the membrane in an anhydrous ethanol solution of 2,5-dichlorop-xylene and keep it at 50 °C - 60 °C for a period of time to complete the cross-linking and quaternization reactions to obtain an AEM membrane.

[0014] ②. Dissolve the PVDF-g-PEI membrane in N,N-dimethylformamide to obtain a PVDF-g-PEI membrane solution.

[0015] ③. Fix the AEM membrane on a frame with a glass plate, then pour the PVDF-g-PEI membrane solution onto the AEM membrane, place it in a vacuum drying oven to dry for a period of time, remove the membrane from the frame with the glass plate, and then immerse the membrane in a hydrochloric acid solution for activation to obtain a shield-type anion exchange membrane with acid resistance performance, and store it in the hydrochloric acid solution.

[0016] Main principle of the present invention:

[0017] Due to the hydrophilic-hydrophobic difference between the main chain and the side chain in the present invention, the membrane material spontaneously forms a microphase separation structure during the film-forming process; this unique microscopic morphology not only ensures the mechanical strength of the membrane but also provides a continuous channel for ion transport; on the other hand, the present invention uses a blend system of PVDF and PEI as the substrate, and through the crosslinking effect of p-xylene dichloride, the quaternization modification of PEI and the construction of a three-dimensional crosslinked network are achieved in one step. Among them, quaternization endows the material with strong alkaline ion exchange ability, while the crosslinked structure significantly improves the dimensional stability of the membrane. This membrane shows in BMED applications that the weak base layer on the surface effectively blocks the penetration of acid molecules, and the strong base crosslinked network at the bottom ensures excellent ion conductivity. The synergistic effect of the two enables the membrane material to maintain stable separation performance during long-term operation.

[0018] Advantages of the present invention:

[0019] 1. The weak base layer on the surface of the present invention effectively blocks the penetration of acid molecules, and the strong base crosslinked network at the bottom ensures excellent ion conductivity;

[0020] 2. The synergistic effect of the crosslinked structure and the surface weak base layer enables the membrane material to maintain stable separation performance during long-term operation;

[0021] 3. The polyamine structure of polyethyleneimine (PEI) meets the requirements of simultaneously achieving crosslinking stabilization and quaternization functionalization, effectively improving the ion exchange capacity;

[0022] 4. Tris(2-pyridylmethyl)amine (TPMA) can form an efficient catalytic system with CuBr2. Description of the drawings

[0023] Figure 1 IEC values of the shield-shaped anion exchange membranes with acid-blocking performance prepared in Examples 1 to 5;

[0024] Figure 2 IEC values measured after taking out the shield-shaped anion exchange membrane with acid-blocking performance prepared in Example 1 and the side-chain-free AEM-8 prepared in Comparative Example 1 after soaking in 1 mol HCl solution for one week. Detailed implementation manners

[0025] Detailed implementation manner 1: A preparation method of a shield-shaped anion exchange membrane with acid-blocking performance in this implementation manner is specifically completed according to the following steps:

[0026] I. Preparation of PVDF-g-PEI:

[0027] ①. Dissolve polyvinylidene fluoride (PVDF), polyethyleneimine (PEI), tris(2-pyridylmethyl)amine (TPMA), and CuBr₂ in a reactor containing N,N-dimethylformamide (DMF). Then add polished copper wire to the mixed solution, introduce nitrogen into the reactor to remove the air in the reactor, and then seal the reactor under a nitrogen atmosphere.

[0028] ②. Place the reactor in a constant-temperature oil bath and heat for a period of time, then immerse it in an ice bath system to terminate the reaction to obtain a reaction mixture. Add the reaction mixture to an ethanol solution for precipitation, filter and remove the remaining polished copper wire to obtain a solid reaction product. Dissolve the solid reaction product in N,N-dimethylformamide, and then add it to an ethanol solution for precipitation for purification, filter, and vacuum dry at room temperature to obtain PVDF-g-PEI.

[0029] II. Preparation of PVDF-g-PEI membrane:

[0030] Dissolve PVDF-g-PEI in N,N-dimethylformamide, then cast it onto a flat glass plate, and then place it in a vacuum oven to dry for a period of time. The membrane will fall off the glass plate. Finally, immerse the membrane in an HCl solution for protonation to obtain a PVDF-g-PEI membrane, and store the PVDF-g-PEI membrane in the HCl solution.

[0031] III. Preparation of anion exchange membrane:

[0032] ①. Dissolve polyvinylidene fluoride and polyethyleneimine in N,N-dimethylformamide, stir for a period of time, then add azobisisobutyronitrile, and then cast it onto a flat glass plate, and then place it in a vacuum oven to dry for a period of time. The membrane will fall off the glass plate. Finally, immerse the membrane in an anhydrous ethanol solution of 2,5-dichlorop-xylene and keep it at 50 °C - 60 °C for a period of time to complete the crosslinking and quaternization reactions to obtain an AEM membrane.

[0033] ②. Dissolve the PVDF-g-PEI membrane in N,N-dimethylformamide to obtain a PVDF-g-PEI membrane solution.

[0034] ③. Fix the AEM membrane on a frame with a glass plate, then pour the PVDF-g-PEI membrane solution onto the AEM membrane, place it in a vacuum drying oven to dry for a period of time, remove the membrane from the frame with the glass plate, and then immerse the membrane in a hydrochloric acid solution for activation to obtain a shield-type anion exchange membrane with acid resistance, and store it in the hydrochloric acid solution.

[0035] The purpose of using polished copper wire in step ① of this embodiment is: suitable for long-term reaction, slow release of CU from the copper wire, avoiding instantaneous excess of monovalent copper leading to explosive polymerization. 0 Release, avoiding instantaneous excess of monovalent copper leading to explosive polymerization.

[0036] In the second step of this embodiment, the film-forming process can induce the microphase separation structure of the hydrophilic and hydrophobic segments, and can also remove by-products and impurities.

[0037] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that: in step ① of step one, the mass ratio of polyvinylidene fluoride, tris(2-pyridylmethyl)amine, CuBr2 and polished copper wire is 6g:20mg:15mg:0.2g; in step ① of step one, the mass-volume ratio of polyvinylidene fluoride, polyethyleneimine and N,N-dimethylformamide is 6g:120mL:(30mL to 50mL). Other steps are the same as those in Specific Embodiment 1.

[0038] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that: in step ② of step one, the volume ratio of absolute ethanol to deionized water in the ethanol solution is 3:1; in step ② of step one, the reactor is placed in a constant temperature oil bath at a temperature of 60°C to 90°C and heated for 8h to 40h. Other steps are the same as those in Specific Embodiment 1 or 2.

[0039] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that: in step ② of step one, the mass ratio of the solid reaction product to the volume of N,N-dimethylformamide is (5g to 7g):(30mL to 50mL). Other steps are the same as those in Specific Embodiments 1 to 3.

[0040] Specific Embodiment 5: The difference between this embodiment and one of Specific Embodiments 1 to 4 is that: in step two, the mass ratio of PVDF-g-PEI to the volume of N,N-dimethylformamide is (5g to 7g):(30mL to 50mL); the concentration of the HCl solution in step two is 0.5mol / L to 2mol / L. Other steps are the same as those in Specific Embodiments 1 to 4.

[0041] Specific Embodiment 6: The difference between this embodiment and one of Specific Embodiments 1 to 5 is that: in step two, PVDF-g-PEI is dissolved in N,N-dimethylformamide, then cast onto a flat glass plate, and then placed in a vacuum oven at 50°C to 60°C and dried for 24h to 28h. The film falls off the glass plate, and finally is immersed in the HCl solution for protonation for 18h to 24h to obtain the PVDF-g-PEI film. Other steps are the same as those in Specific Embodiments 1 to 5.

[0042] Specific Embodiment Seven: The difference between this embodiment and any one of Specific Embodiments One to Six is as follows: In step 3①, the mass-volume ratio of polyvinylidene fluoride, polyethyleneimine, N,N-dimethylformamide, and azobisisobutyronitrile is 5 g: 120 mL: 50 mL: 0.02 g; the stirring time in step 3① is 2 h to 3 h. Other steps are the same as those in Specific Embodiments One to Six.

[0043] Specific Embodiment Eight: The difference between this embodiment and any one of Specific Embodiments One to Seven is as follows: In step 3①, it is dried in a vacuum oven at 50 °C to 60 °C for 10 h to 12 h; the holding time at 50 °C to 60 °C in step 3① is 20 h to 24 h; the concentration of the anhydrous ethanol solution of 2,5-dichlorop-xylene in step 3① is 0.05 mol / L. Other steps are the same as those in Specific Embodiments One to Seven.

[0044] Specific Embodiment Nine: The difference between this embodiment and any one of Specific Embodiments One to Eight is as follows: In step 3②, the mass-volume ratio of the PVDF-g-PEI membrane to N,N-dimethylformamide is (5 g to 7 g): (30 mL to 50 mL); in step 3③, the thickness of the AEM membrane in the shield-type anion exchange membrane with acid resistance is 50 to 80 microns, and the thickness of the PVDF-g-PEI membrane is 70 to 120 microns. Other steps are the same as those in Specific Embodiments One to Eight.

[0045] Specific Embodiment Ten: The difference between this embodiment and any one of Specific Embodiments One to Nine is as follows: In step 3③, the AEM membrane is fixed on a frame with a glass plate, then the PVDF-g-PEI membrane solution is poured onto the AEM membrane, and it is dried in a vacuum drying oven at 50 °C to 60 °C for 24 h to 48 h. The membrane is taken off the frame with the glass plate, and then the membrane is immersed in a hydrochloric acid solution with a concentration of 2 mol / L for activation for 18 h to 24 h to obtain a shield-type anion exchange membrane with acid resistance, which is stored in a hydrochloric acid solution with a concentration of 0.5 mol / L. Other steps are the same as those in Specific Embodiments One to Nine.

[0046] The following examples are used to verify the beneficial effects of the present invention:

[0047] Example 1: A preparation method of a shield-type anion exchange membrane with acid resistance is specifically completed according to the following steps:

[0048] I. Preparation of PVDF-g-PEI:

[0049] ①. Dissolve 6 g of polyvinylidene fluoride, 120 mL of polyethyleneimine, 20 mg of tris(2-pyridylmethyl)amine, and 15 mg of CuBr₂ in a reactor containing 50 mL of N,N-dimethylformamide. Then add a polished copper wire with a length of 10 cm and a mass of 0.2 g to the mixed solution. Introduce nitrogen into the reactor for 1 h to remove the air in the reactor, and then seal the reactor under a nitrogen atmosphere.

[0050] ②. Place the reactor in a constant-temperature oil bath at 60 °C and heat for 8 h, then immerse it in an ice bath system to terminate the reaction, obtaining a reaction mixture. Add the reaction mixture to an ethanol solution for precipitation, filter and take out the remaining 0.1433 g of polished copper wire to obtain a solid reaction product. Dissolve the solid reaction product in 50 mL of N,N-dimethylformamide, then add it to an ethanol solution for precipitation for purification, filter, and dry in vacuum at room temperature to obtain PVDF-g-PEI.

[0051] In the ethanol solution described in step ② of step one, the volume ratio of absolute ethanol to deionized water is 3:1.

[0052] II. Preparation of PVDF-g-PEI membrane:

[0053] Dissolve 5 g of PVDF-g-PEI in 50 mL of N,N-dimethylformamide, then cast it onto a flat glass plate, and then place it in a vacuum oven at 50 °C and dry for 24 h. The membrane falls off the glass plate. Finally, immerse the membrane in a 2 mol / L HCl solution for protonation for 24 h to obtain a PVDF-g-PEI membrane, and store the PVDF-g-PEI membrane in a 0.5 mol / L HCl solution.

[0054] III. Preparation of anion exchange membrane:

[0055] ①. Dissolve 5 g of polyvinylidene fluoride and 120 mL of polyethyleneimine in 50 mL of N,N-dimethylformamide, stir for a period of time, then add 0.02 g of azobisisobutyronitrile, and then cast it onto a flat glass plate. Then place it in a vacuum oven at 60 °C and dry for 10 h. The membrane falls off the glass plate. Finally, immerse the membrane in an absolute ethanol solution of 2,5-dichlorop-xylene and keep it at 50 °C for 24 h to complete the cross-linking and quaternization reactions to obtain an AEM membrane.

[0056] In the absolute ethanol solution of 2,5-dichlorop-xylene described in step ① of step three, the concentration is 0.05 mol / L.

[0057] ②. Dissolve the PVDF-g-PEI membrane in N,N-dimethylformamide to obtain a PVDF-g-PEI membrane solution.

[0058] In Step 3 ②, the mass-to-volume ratio of the PVDF-g-PEI membrane to N,N-dimethylformamide is 5 g:50 mL;

[0059] ③ Fix the AEM membrane on a frame with a glass plate, then pour the PVDF-g-PEI membrane solution onto the AEM membrane, place it in a vacuum drying oven at 50 °C for drying for 48 h, remove the membrane from the frame with the glass plate, and then immerse the membrane in a 2 mol / L hydrochloric acid solution for activation for 24 h to obtain a shield-type anion exchange membrane with acid resistance (denoted as AEM-8), and store it in a 0.5 mol / L hydrochloric acid solution;

[0060] In the shield-type anion exchange membrane with acid resistance described in Step 3 ③, the thickness of the AEM membrane is 70 microns, and the thickness of the PVDF-g-PEI membrane is 110 microns.

[0061] Example 2: The difference between this example and Example 1 is that in Step 1 ②, the reactor is placed in a constant-temperature oil bath at 60 °C and heated for 16 h, and then immersed in an ice bath system to terminate the reaction to obtain a reaction mixture; the shield-type anion exchange membrane with acid resistance obtained in Step 3 ③ is denoted as AEM-16. Other steps and parameters are the same as those in Example 1.

[0062] Example 3: The difference between this example and Example 1 is that in Step 1 ②, the reactor is placed in a constant-temperature oil bath at 60 °C and heated for 24 h, and then immersed in an ice bath system to terminate the reaction to obtain a reaction mixture; the shield-type anion exchange membrane with acid resistance obtained in Step 3 ③ is denoted as AEM-24. Other steps and parameters are the same as those in Example 1.

[0063] Example 4: The difference between this example and Example 1 is that in Step 1 ②, the reactor is placed in a constant-temperature oil bath at 60 °C and heated for 32 h, and then immersed in an ice bath system to terminate the reaction to obtain a reaction mixture; the shield-type anion exchange membrane with acid resistance obtained in Step 3 ③ is denoted as AEM-32. Other steps and parameters are the same as those in Example 1.

[0064] Example 5: The difference between this example and Example 1 is that in Step 1 ②, the reactor is placed in a constant-temperature oil bath at 60 °C and heated for 40 h, and then immersed in an ice bath system to terminate the reaction to obtain a reaction mixture; the shield-type anion exchange membrane with acid resistance obtained in Step 3 ③ is denoted as AEM-40. Other steps and parameters are the same as those in Example 1.

[0065] Measurement of IEC:

[0066] The shield-type anion exchange membranes with acid resistance prepared in Examples 1-5 were successively immersed in deionized water and 0.5 mol / L HCl solution for 24 h respectively to make them completely protonated. Then the membranes were immersed in 1 mol / L KNO3 solution (500 mL) for 48 hours to combine the functional groups on the membranes with NO3 - After rinsing the free NO3 on the membrane surface with a large amount of deionized water, the membranes were immersed in 0.2 mol / L NaCl solution (500 mL) for 48 hours. The concentration of NO3 in the solution was measured using an ultraviolet spectrophotometer at a wavelength of 210 nm, and the number of moles of NO3 exchanged by Cl- was calculated, as shown in - - - Figure 1 shown;

[0067] It can be seen from Figure 1 that the ion exchange capacity of the shield-type anion exchange membranes with acid resistance prepared in Examples 1-5 shows a typical saturated growth trend with the exchange time: the cross-linked network gradually relaxes and the ion channels open at 8-16 h, and the adsorption amount of NO3 - increases. The subsequent growth is too slow because the adsorption approaches the equilibrium state, the quaternization sites are saturated, and the absorbance growth rate slows down.

[0068] Comparative Example 1: The preparation method of a traditional anion exchange membrane was specifically completed according to the following steps:

[0069] 6 g of polyvinylidene fluoride and 120 mL of polyethyleneimine were dissolved in 50 mL of N,N-dimethylformamide, continuously stirred for 2 h, 0.02 g of azobisisobutyronitrile was added, and then cast onto a flat glass plate. Then it was placed in a vacuum oven at 60 °C and dried for 10 h. The membrane peeled off from the glass plate. Finally, the membrane was immersed in an anhydrous ethanol solution of 2,5-dichlorop-xylene, and the concentration of the anhydrous ethanol solution of 2,5-dichlorop-xylene was 0.05 mol / L; it was kept at 50 °C for 24 h to complete the cross-linking and quaternization reactions. In addition, the membrane was kept in a vacuum oven at 50 °C for more than 48 h to completely evaporate the solvent. Finally, the membrane was immersed in 2 mol / L hydrochloric acid solution for 24 h to obtain a side-chain-free anion exchange membrane (denoted as side-chain-free AEM-8).

[0070] Figure 2 Shown are the IEC values measured after the shield-type anion exchange membrane with acid resistance prepared in Example 1 and the side-chain-free AEM-8 prepared in Comparative Example 1 were taken out after being immersed in 1 mol HCl solution for one week.

[0071] It can be seen from Figure 2 ​​​It can be seen that: due to soaking for one week under acidic conditions, the IEC content of the membrane without side chains decreased due to the loss of quaternary ammonium groups, indicating that the surface microphase structure can effectively reduce the influence of acidic conditions. However, due to the presence of a strong alkaline cross-linked structure, the decrease in IEC content is not obvious.

Claims

1. A preparation method of a shield-type anion exchange membrane with acid resistance performance, characterized in that The preparation method is specifically completed according to the following steps: I. Preparation of PVDF-g-PEI: ①. Dissolve polyvinylidene fluoride, polyethyleneimine, tris(2-pyridylmethyl)amine, and CuBr2 in a reactor containing N,N-dimethylformamide. Then add polished copper wire to the mixed solution, introduce nitrogen into the reactor to remove the air in the reactor, and then seal the reactor under a nitrogen atmosphere. ②. Place the reactor in a constant-temperature oil bath and heat for a period of time, then immerse it in an ice bath system to terminate the reaction, obtaining a reaction mixture. Add the reaction mixture to an ethanol solution for precipitation, filter and remove the remaining polished copper wire to obtain a solid reaction product. Dissolve the solid reaction product in N,N-dimethylformamide, and then add it to an ethanol solution for precipitation for purification, filter, and vacuum dry at room temperature to obtain PVDF-g-PEI. II. Preparation of PVDF-g-PEI membrane: Dissolve PVDF-g-PEI in N,N-dimethylformamide, then cast it onto a flat glass plate, and then place it in a vacuum oven to dry for a period of time. The membrane will fall off the glass plate. Finally, immerse the membrane in an HCl solution for protonation to obtain a PVDF-g-PEI membrane, and store the PVDF-g-PEI membrane in the HCl solution. III. Preparation of anion exchange membrane: ①. Dissolve polyvinylidene fluoride and polyethyleneimine in N,N-dimethylformamide, stir for a period of time, then add azobisisobutyronitrile, and then cast it onto a flat glass plate. Then place it in a vacuum oven to dry for a period of time. The membrane will fall off the glass plate. Finally, immerse the membrane in an anhydrous ethanol solution of 2,5-dichlorop-xylene and keep it at 50°C - 60°C for a period of time to complete the cross-linking and quaternization reactions to obtain an AEM membrane. ②. Dissolve the PVDF-g-PEI membrane in N,N-dimethylformamide to obtain a PVDF-g-PEI membrane solution. ③. Fix the AEM membrane on a frame with a glass plate, then pour the PVDF-g-PEI membrane solution onto the AEM membrane, place it in a vacuum drying oven to dry for a period of time, remove the membrane from the frame with the glass plate, and then immerse the membrane in a hydrochloric acid solution for activation to obtain a shield-type anion exchange membrane with acid resistance, and store it in the hydrochloric acid solution.

2. The preparation method of a shielded anion exchange membrane with acid resistance according to claim 1, characterized in that In step I①, the mass ratio of polyvinylidene fluoride, tris(2-pyridylmethyl)amine, CuBr2, and polished copper wire is 6g:20mg:15mg:0.2g; in step I①, the mass-volume ratio of polyvinylidene fluoride, polyethyleneimine, and N,N-dimethylformamide is 6g:120mL:(30mL - 50mL).

3. The preparation method of a shielded anion exchange membrane with acid resistance according to claim 1, characterized in that In step I②, the volume ratio of absolute ethanol to deionized water in the ethanol solution is 3:1; in step I②, place the reactor in a constant-temperature oil bath at 60°C - 90°C and heat for 8h - 40h.

4. The preparation method of a shield-type anion exchange membrane with acid resistance according to claim 1, characterized in that In step I②, the mass-volume ratio of the solid reaction product to N,N-dimethylformamide is (5g - 7g):(30mL - 50mL).

5. The preparation method of a shielded anion exchange membrane with acid resistance according to claim 1, characterized in that The mass-volume ratio of PVDF-g-PEI described in Step 2 to N,N-dimethylformamide is (5 g - 7 g):(30 mL - 50 mL); the concentration of the HCl solution described in Step 2 is 0.5 mol / L - 2 mol / L.

6. The preparation method of a shield-type anion exchange membrane with acid resistance according to claim 1, characterized in that In Step 2, PVDF-g-PEI is dissolved in N,N-dimethylformamide, then cast onto a flat glass plate, and then placed in a vacuum oven at 50°C - 60°C for drying for 24 h - 28 h. The film detaches from the glass plate and is finally immersed in the HCl solution for protonation for 18 h - 24 h to obtain a PVDF-g-PEI membrane.

7. The preparation method of a shield-type anion exchange membrane with acid resistance according to claim 1, characterized in that The mass-volume ratio of polyvinylidene fluoride, polyethyleneimine, N,N-dimethylformamide, and azobisisobutyronitrile described in Step 3① is 5 g:120 mL:50 mL:0.02 g; the stirring time described in Step 3① is 2 h - 3 h.

8. The preparation method of a shielded anion exchange membrane with acid resistance according to claim 1, characterized in that In Step 3①, it is placed in a vacuum oven at 50°C - 60°C for drying for 10 h - 12 h; the holding time at 50°C - 60°C in Step 3① is 20 h - 24 h; the concentration of the anhydrous ethanol solution of 2,5-dichlorop-xylene described in Step 3① is 0.05 mol / L.

9. The preparation method of a shield-shaped anion exchange membrane with acid resistance according to claim 1, characterized in that The mass-volume ratio of the PVDF-g-PEI membrane described in Step 3② to N,N-dimethylformamide is (5 g - 7 g):(30 mL - 50 mL); the thickness of the AEM membrane in the shield-type anion exchange membrane with acid resistance described in Step 3③ is 50 - 80 microns, and the thickness of the PVDF-g-PEI membrane is 70 - 120 microns.

10. The preparation method of a shield-type anion exchange membrane with acid resistance according to claim 1, characterized in that In Step 3③, the AEM membrane is fixed on a frame with a glass plate, then the PVDF-g-PEI membrane solution is poured onto the AEM membrane, placed in a vacuum drying oven at 50°C - 60°C for drying for 24 h - 48 h, the membrane is taken off the frame with the glass plate, and then the membrane is immersed in a hydrochloric acid solution with a concentration of 2 mol / L for activation for 18 h - 24 h to obtain a shield-type anion exchange membrane with acid resistance, and it is stored in a hydrochloric acid solution with a concentration of 0.5 mol / L.

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